A.J. Burnett was a big reason why a Pittsburgh Pirates franchise that was at or near the bottom of the league standings ended a 21-year postseason drought in 2013.

Now the well-traveled veteran is in a position once familiar to Pirates fans - last place - in his first season with the Philadelphia Phillies.

He returns to Pittsburgh on Sunday to face good friend Jeff Locke as he tries to help the lowly Phillies avoid their first three-game sweep in the Steel City in 12 years.

Burnett (5-7, 3.92 ERA) spent his previous two seasons with the Pirates, leading the 2012 club with 16 wins and going 10-11 with a 3.30 ERA last year as Pittsburgh won 94 games and lost to eventual NL champion St. Louis in a division series.

"Coming here and coming to a place where there was a young crew and being one of the older guys, I still give all my thanks to the guys in that locker room and what they thought of me from day one, and even today," Burnett told MLB's official website. "We stay in touch. It's a special group."

The 37-year-old Burnett was leaning toward retirement before signing a two-year deal with Philadelphia (37-50) in which he will make $33.5 million if he makes 30 starts or more in both years.

Burnett has pitched more innings than any Philadelphia pitcher, and there are rumors that he could be on the trading block. Pittsburgh (46-41), which didn't extend a $14.1 million qualifying offer to Burnett prior to the start of free agency, is considered a prime candidate for his services.

The right-hander's old team is surging into contention while winning 11 of 14. The Pirates last swept the Phillies from April 19-21, 2002, and they've yet to sweep anyone in 2014.

Burnett will return to town to square off with a Pirates pitcher who looked up to him in Locke (1-1, 3.46), who went 2-0 with a 1.54 ERA in two starts against the Phillies last year.

"I think it's going to be a lot of fun," Locke said. "No different than any other game, I know A.J.'s going, no different than I'm going for us. It's going to be a lot of fun. I'm sure there's a lot more pressure on him than there is me, that's for sure."

The Pirates have won the last four starts by the left-hander, who gave up two runs in eight innings and did not get a decision in Tuesday's 3-2 win over Arizona.

Jimmy Rollins is 0 for 6 against Locke while Burnett has never faced the Pirates' top six leaders in at-bats.

That group of Pittsburgh hitters includes superstar Andrew McCutchen, who is 9 for 17 with five RBIs in his last four games. Jordy Mercer, who is 4 for 6 with four RBIs in this series and 9 for 14 in his last five games, has also never faced Burnett.

McCutchen hit a two-run homer in Saturday's 3-2 win after he had four hits in Friday's 8-2 rout. The Phillies fell behind 3-0 after two innings Saturday after trailing 4-0 after one Friday.

"We haven't been able to bounce back from being down early in the game," manager Ryne Sandberg said.

Rollins and Ryan Howard are each 0 for 6 in the series for the Phillies, losers of eight of nine.